fuel pump stays on with key on

[lurker01]

93 Explorer (only one motor that year). When i turn the key on (not the engine) the fuel pump comes on (as it should), but does not shut off. When I start the car (it does start after a few attempts), the idle is erratic and the car shuts off after a short period of time. Check Engine Light stays on. When driving, the car stalls, bucks, etc. I replaced the fuel pump relay - no go, same issue. I went to the junk yard yesterday and picked up several different parts (Map [or Maf] sensor and fuel pressure regulator, among other parts).

Anyone have any ideas about what is causing this issue?? I would love some help.

"Some Days It's Just Not Worth Chewing Through The Restraints.."

 

[Maniak]

Since the pump is constantly running, I'm guessing either the pump is bad or maybe the FPR is bad resulting in low pressure.

Grab a fuel pressure tester gauge and check the pressure at the fuel rail.

~Mark

 

[lurker01]

i'll buy one on the way home....i know where to attach a fuel pressure tester, but what should the pressure be..about?

"Some Days It's Just Not Worth Chewing Through The Restraints.."

 

[Maniak]

IIRC, around 32-35 at idle. Also, it should hold pressure when you turn off the vehicle. IF it doesn't, you have a leak somewhere.. Either its the check valve on the pump, bad fuel pressure regulator, or a leaking injector.

Also, search the useful thread sub forum and search for fuel. There are a couple good threads there about testing fuel pressure

~Mark

 

[lurker01]

I will do that...I hope it's the fuel pressure regulator - i picked up two of those at the junkyard yesterday.....

how do you tell if an injector is leaking? Will there be fuel pooling somewhere? I don't smell any fuel..

"Some Days It's Just Not Worth Chewing Through The Restraints.."

 

[Maniak]

If an injector is leaking, turn the key on (not the engine), let it sit like that for a few minutes and look around the top of the engine. If you don't see any fuel there, pull the plugs and see if any are wet? If so, that injector is leaking.

Edit: You can actually just pull the all the plugs and do the above test. Then turn it over.. the Cylinder with the leaking injector will shoot gas out the hole when you turn it over.

~Mark

 

[lurker01]

Well, been working on it after work the past few days.
Changed the fuel pump relay twice.
Checked all vacuum hoses I could find.
Changed the fuel pressure regulator.
Changed the fuel filter.
Working on borrowing a fuel pressure gauge from a friend.
Have not checked the injectors yet - this weekend.
Starting to look like I'm gonna drop the fuel tank.....we'll see.
Any good ideas about how to drain the fuel tank? I don't have a pump..


"Some days it's just not worth chewing through the restraints.."

 

[Punjab]

Don't drop the tank!

There's a thread on here that details how to cut an access hatch in the floor just above the fuel tank to access the pump and sending unit. I believe its stickied, possibly at the top of this section of the forum.
Saves hours of your time and much less hassle.

 

[tk1251k]

Check the eec relay I had the problem you are having . The eec relay controls the fuel pump relay also..

 

[lurker01]

i have changed it twice - same results....

"Some Days It's Just Not Worth Chewing Through The Restraints.."

 

[lurker01]

All right - long day.

Replaced the fuel pump relay again - no luck.

Pulled all 6 plugs - 5 were covered in black carbon/soot. Only one was light brown - as it should be. None were wet.

Rented a fuel pressure gauge from Auto Zone ($150) - pressure with key on (not the motor) - reached 40 pounds and stayed there. Turned key off - stayed there - no drop in pressure...... Darn - I was actually hoping it would drop. Bled pressure off and did it again 3 or 4 times. Same results..hmmmm..


Took power distribution box loose and checked for any loose/burned wires - looks ok...

Pulled fuel line off of fuel filter (tank side) - turned key on - plenty of gas coming out. So, the fuel pump comes on, stays on, fuel reaches fuel filter (new) at least. OK, now what?

By the way, the car does not start now... for whatever reason....

I'm thinking - I read somewhere - that there is a PCM (this is the vehicle computer, correct?) relay somewhere...Where? Manual does not mention it that I can find....

Then, I'm thinkin', I'll go to the junkyard and get a PCM (there's a care there in good shape that has only been there a couple of days) and swap it out just, well, just to try something else.

Any good ideas out there? By the way, I can take anything apart and put it back together, but I'm a moron when it comes to electrictiy....

"Some days it's just not worth chewing through the restraints.."

 

[tk1251k]

Can you still hear the fuel pump come on. Did you check the computer relay in the distribution box . Also check the 30 amp large blade fuse in the distribution box. Mine blew while driving a few weeks ago after having it towed 50 miles I found the 30 amp large blade fuse was blown which also controls the fuel pump. I did alot of research on here while my 94 explorer was being towed so when it arrived bingo what I suspected. May not be your problem but something else to check. Mine just shut down on interstate very sudden.

 

[lurker01]

fuel pump come on and stays on
relay changed several times
fuse is good

"Some days it's just not worth chewing through the restraints.."

 

[tk1251k]

I would change the relays around the fuel pump and eec realy with others they should all be the same. I bought 2 at separate times once at autozone both bad fuel pump would not shut off. Went to dealer got one worked worked fine so they can be bad even new ones. I would change those relays around to make sure again.

 

[YBCold]

i had a key off battery drain i traced to the EEC relay i think it kept the pump running or atleast primed it after i shut the engine off. could be another thing to look at not 100% sure but thought id share

 

[lurker01]

Yeah, I've read that the EEC relay and the Fuel Pump Relay are tied together somehow - so I changed that relay also!

"Some days it's just not worth chewing through the restraints.."

 

[lurker01]

Well, almost there.
Went to the junk yard and found a 1994 Explorer (mine is a '93) - pulled the PCM out ($28), took it home, plugged it in to my car. Turned the key on - fuel pump came on and went off after about 2-3 seconds!!! Perfect! Started it up. Idles a little rough - little bit of black smoke coming out of the tail pipe - guess it's running a little rich. Check Engine light came on after about 4 seconds. Drove around - got it up to about 50 mph - runs fine, but idles a little rough and CEL stays on. When I turn the car off and restart it, CEL comes back on after a few seconds... So, I am going to check all my vacuum hoses tomorrow and the big plastic air intake 'thing.'


"Some days it's just not worth chewing through the restraints.."

 

[Maniak]

Since you have a CEL, check the code.. BUT, my guess is its the Cam sensor or EGR since the 1994 has both and the 1993 doesn't. I can't remember which on the 1993 is missing though.

~Mark

 

[tk1251k]

B sure to check underside of big plastic air intake especially where it connects to maf mine had three rather large slits overtime there from rubbing something idle kept getting worse taped it shut no more idle problem for now anyway.

 

[lurker01]

Drove it to work today - drives fine other than the rough idle.
I plan on taking it over to Advance or AutoZone today or tomorrow to see what code(s) it's giving..

I checked the air intake tube yesterday - seems to be tight..... but I'll tape it.

I think the 94 has an EGR valve, could never find one on mine - that might be the issue. Any way around that?


"Some days it's just not worth chewing through the restraints.."